Method and composition of producing fine lines photographically



menge-.1 1.,.. 29, 1946 2,393,821l

bases.

In general, hydrouoric all mixture is heated tothe boiling point, forexample, in a double boiler. When the albumen has completely coagulatedand the solution cooled lclown to room temperature. it is iiltered.'I'he speelde weight o! the clear nltered solution is about 1.04. Thissolution is hereinbelow referred to as photo-engraver's glue solution.

An llbumen solution comprising 2i) gms. of dry albumen and 100 cc. ofdistilled water is preli'ed. The llbumen is soaked in the water forlbellt four hours and to the resulting solution is then added a smallamount, for example, two drops o! Phenol l' other suitable preservative.The solution is then iiltered through cotton.

A solution comprising 4 gms. of ammonium biohromate and 1.00 cc. ofdistilled water is pre- Pared.

A. solution comprising 40 gms. of tannic acid and 100 ce. of distilledwater is prepared by dissolving the tannic acid in the water with the:1d of heat and then cooling to room temperaille.

To prepare the sensitizing solution, three parts of the above preparedphotoengravers glue solution. onepart of the albumen solution and onepart o! the ammonium bichromate solution are mixed thoroughly and thenfiltered. care being taken to carry out the mixing away from directlight and air as much as possible. However. oonduoting the preparationin a darkroom is not necessary.

A piece or Plate of chemically cleaned and polished :lass or othermaterial on which the nne lines are te be Produced is then coated with athin coating o! the sensitizing solution. Any well-known coating methodmay be utilized for this purpose. such as centrifugal coating. smearmethod, painting or other satisfactory coating procedure. The coatedplate is then allowed to dry in the absence of extreme heat, directsunlight and air currents. avoiding dust as much as possible. In thisway, a light-sensitive chrol mate colloid layer is produced on thesurface.

The scales or ne lines are obtained by exposing the sensitive layer tolight through a fine line negative. For example, the exposure may bemade through a contrasty negative of the fine ,lines to be obtained,using a 25 ampere arc lamp at two feet distance the exposure time being2-3 minutes depending on the negative. 'I'his is only given as anexample, and other times of exposure and types oi exposure light may beutilized. To develop the image ell that i! necessary is to immerse theplate in a tepid water bath or wash 'under running water for liveminutes. Care must Y or casein may be utilized in the process incorresponding amounts. Likewise, instead of ammonium biohromate, theremay be used potassium or sodium blohrornate in equivalent amounts. Thealbumen lmay be omitted but improved re.- Sults are obtained,particularly with respect to ladhesion, when it is present in thelight-sensitive ayer.

The above embodiment` of the process results f in the production of nnelines and the products so obtained may be used directly as graticules.scales and cross hairs for technical and other purposes.

In the alternative embodiment, the une lines are utilized as resists inthe production oi' etched lines, scales and graticules on glass or onother inorganic bases such as copper. In photo-engrav ing and relatedprocesses where the image is etched into the base material', the chiefproblem' is to 11nd a resist which will withstand a certain amount ofmechanical abrasion, adhere to the base and be impervious to the etchingsolution which is usually acidic in character. As pointed out above,some acids like hydroiluoric and its salts penetrate the usualphotoengraving resists with ease and cannot be used when a photographicdesign has to be etched on glass, For this reason, the priorphotoengraving resists cannot be used to produce tine lines by etchinii.

The prior art processes are unsatisfactorybecause in transferring veryiine lines to glass Aor other base, the reslstmust of necessity be verythin in order to faithfully reproduce the tine details of the originalwhich consists mostly oi' very ne lines, dashes or dots. Since the usualphO- toengraving resists are attacked by the 'acidic etching iiuids,these line lines are quicklyattacked and the' etched lines produced arenot of high resolution but are ragged and not clearly defined.

For the production of line lines, the resolving power of thelight-sensitive coating must be extremely high to insure the faithfulreproduction of microscopic detail. A photoengraving resist shouldpreferably have a dark color winch facilitates inspection prior to theapplication'of'the etching uid.

In our alternative embodiment of producing fine lines, the samesolutions and procedurear'e employed as in the iirst embodiment. exceptthat for exposure, a contrasty positive is used to obtain a negativeimage of fine lines on the sensitized coating: that is. the image iswashed away.

be `taken to insure that all unexposed sensitized material is washedaway.

After developing, the plate is immersed for nve minutes in the tannioacid solution. It is then again careiully washed. followed by a rinse ini dithled water. The plate is then allowed to dry and the image is thenhat-carbonized by exposing to heat until the maximum blackness of theimage is obtained. Good results are obtained when an exposure at l450 F.for 30 minutes is utilised although other temperatures and periods ofheating give equally good results. The fine lines so produced withstandthe action of hydroiiuoric acid and its salts. The lines also areresistant to abrasion and various solvents and cleaning uids such asxylol. The lines show excellent resolution and the absence of graininessand roughness of edges common to prior methods of producing fine lines.

Although we prefer to use iish glue, gelatin leaving the surroundingarea protected. Subsequent to the tannio acid treatment and carbonicing,the resist is dark in color which facilitates inspection and has greatresistance to mechanical abrasion and to the selected etch. The plate isthen treated with an appropriate etch which acts only in the area. ofthe image, the resist, due to the tannic acid and subsequent bakingtreat- `ment, possessing the novel property of withstanding the actionof hydroiiuoric acid and its salts. After the lines have been etched inthe surface, the resist is then removed. The etched lines may then befilled in hy use of any suitable black varnish.

By way of example, a more detailed of this embodiment follows:

A glass plate chemically cleaned and polished is coated with thesensitizing solution prepared in the manner indicated in Example I. Thecoated plate is then exposed through a contrasty positive of the nelines to be etched on the description glass base, and subsequentlytreated as in Example I with tannic acid, followed byheat-carbonization. The plate 'with the carbonized areas thereon actingas a resist is then treated with an etching solution' of the followingcomposition: Ammonium bifluoride -grams-.. Barium sulfate --dolinesmaybe filled in by the use of a suitable black varnish or any othersuitable preparation.

The following is an example of the procedure as applied to theprcductionof etched lines on a metal plate, such as copper:

Example III The resist is prepared on a copper .plate in the same manneras described in Example II above for its preparation on glass. 'Ihe areaof the image is then treated with a Baume solution of ferric chlorideuntil the desired degree of etch is obtained. The resist is then removedby rubbing the plate with calcium carbonate.

In the -above example of etching glass, any

glass etching fluid may be utilized although ithe process is mosteffective with the use of ammonium bifiuoride. However, hydrofluoricacid or any of its water soluble salts may also be used. Likewise, otheretching fluids may lbe used for etching the copper or metal surfaces.

While several embodiments of the invention are herein described, it isto be understood that various modifications may be apparent to thoseskilled in the artrwithout departing from the spirit and scope of thisinvention and we, therefore, do not wish to be hunted by the precisedetails set forth, but desire to avail ourselves of such variations andmodifications as come within the scope of the appended claims.

We claim: I

l. A method of producing cross-hairagraticules, scales and designs withfine lines on surfaces, which comprises coating a surface with alight-sensitive chromate colloid layer in which the colloid is selectedfrom the group consisting of fish glue, casein and gelatin, exposing thelayer to a light-projected image of fine lines, removing the unexposedareas of the layer, subjecting the exposed areas to a tannicacid-containing substance, and subjecting the tannic acid-treated areasof the layer to a heat-carbonizing treatment, whereby fine lines of highresistance to abrasion and chemical agencies, and high resolution,adhesion and density are obtained.

2. A process as in claim 1 in which the surfac is glass.

3. A method of producing cross-hairs, graticules, scales and designswith fine lines on a glass surface which comprises coating a glass bodywith a light-sensitive solution composed of fish glue, albumen andammonium bichromate, exposing the light-sensitive layer. thus formedthrough a negative of the fine lines to be obtained, removing theunexposed areas of the layer by developingnwith water, subjecting theexposed areas of the layer to an aqueous `solution of tannic acid, andsubjecting the tannic acid treated areas of the layer to aheat-carbonlzing treatment until maximum blackness of the exposed areasis obtained, whereby fine lines of'high resistance to abrasion andchemical agencies, and high resolution, adhesion and density areobtained.`

4. A process as in claim 3 in which the carbo izlng treatment is carriedout by subjecting the tannic'acid treated areas .to a temperature ofabout 450 F. for about thirty minutes.

5. A process for producing cross-hairs, graticules, scales and designswithv fine lines on surfaces which comprises coating a surface with alight-sensitive chromate colloid layer in which the colloid is selectedfrom the group consisting of nsh glue, casein and gelatin. exposing thelayer through a positive of the fine lines to be obtained, removing theunexposed areas of the layer, subjecting the exposed areas to a tannicacid-containing substance, subjecting the tannic acid-treated areas ofthe layer to a heat-carbonizingtreatment, thereby converting the exposedareas into a resist, and subjecting to an ,etching solution those areasof the vsurface from i into a resist, and subjecting to an aqueous etch-Ding solution composed of ammonium bifiuoride and barium sulfate thoseareas of the glass surface from which the unexposed areas of theiightsensitive layer has been removed, and then removing the resist.

A '1. A process as in claim 6 in which the surface is composed of copperand in which the etching is carried out by means of an aqueous ferriechloride solution.

8. A composition for producing flnelines and resists for etching of finelines on surfaces which comprises the heat-carbonized reaction productof a tannic acid-treated, light-exposed mixture of a protein selectedfrom the group consisting of fish glue, casein and gelatin, and alight-sensitive chromate, said composition being resistant tohydrofiuoric acid and its salts.

9. A new resist for photoetching of fine lines on surfaces comprisingthe heat-carbonized reaction product of a tannic acid-treatedlight-exposed mixture of fish glue, albumen and ammonium bichromate,said composition being re sistant to hydrofiuoric acid and its salts.

i9. A composition for use in preparing a resist for photoetching of finelines on surfaces comprising the reaction product of a protein selectedfrom the group consisting of fish glue,

gelatin and casein and a light-sensitive bichromate, said composition,on exposure to light and subsequent treatment with tannic acid followedby heat-carbonization, forming a resist which will withstand the actionof hydrouoric acid and its salts. n

11. A body having on its surface line lines,

cross-hairs, scales andgraticules composed of the heat-carbonizedreaction product of a tannic acid-treated and li8ht-exposed mixture ot achromate said reaction product being resistant to hydrotiuoric acid andits salts.

12. A body having on its surface me lines, cross-hairs. scales andmticules composed ot 6 acid and its salts.

the heat-carbonized reaction product of a tannic acid-treated,light-exposed mixture of iish glue, albumen and ammonium bichromate saidreaction product being resistant to hydrofluoric ANDR scHoEN. LETHALEMON PAmnsoN.

